The prior art discloses laser based aids to navigation, with particular application to landing, which use a series of low power visible lasers to illuminate corridors of sky which define the proper approach path. In the basic embodiment the system uses three colors: Amber (or yellow) to indicate on course, red to indicate left of course, and green to indicate right of course. In addition when well left or right of course the colors are made to blink, first slow and then fast.
There are two such systems. One defines the extended centerline of the landing area and the other defines the proper glideslope. In practice there are aspects of the basic design which are not optimal, and specific additions and delineations which improve the overall performance of the system are desirable. In particular, it is possible for the flashing corridors to become confused with aircraft beacons or other flashing lights which are known to be found in the vicinity of the approach corridor. Also, modifications to the corridor size produce better approach performance by optimizing the match between corridor size and aircraft flight characteristic. Further, light scattering from the lens of the exit aperture of the current art design can cause distractions to the pilot during the final stages of the approach. Still further, modifications to the basic design disclosed in this patent provide for greater ease in maintenance by allowing easy and exact replacement of laser which is necessary due to the limited lifetime of the laser, and changes to the optical design allows for easier and more cost effective manufacturing.